1. Field of the Invention
The present invention generally relates to a control system for auxiliary equipment for vehicles. More particularly, it relates to a control system for auxiliary equipment for vehicles which are driven by engine power.
2. Description of Relevant Art
There are varieties of control system of the type that are engine driven which control, in conjunction with the state of acceleration of an engine, auxiliary equipment for vehicles, such as an air conditioner compressor for cooling.
Exemplarily, Japanese Patent Publication No. 47-10721, published on Mar. 31, 1972, discloses a control system which permits part of the engine power to be supplied to an air conditioner compressor for cooling a vehicle while an acceleration pedal is depressed and exceeds a predetermined stroke thereof, or another state such that a carburetor intake pipe has a negative inner pressure attendant such as when the vehicle is travelling on a downward slope.
In such a control system, however, since the cooling oriented air conditioner, which generally consumes a lot of energy when operating, is supplied with the operating energy from an engine with limited output energy capacity, the engine power originally intended to propel the vehicle is even more reduced, so that the ability to accelerate decreased.
For such a reason, conventionally, there have already been proposed a number of control systems of a type to stop the operation of a compressor by detecting the state of acceleration of the vehicle.
For example, Japanese Utility Model Publication No. 51-41315, published on Oct. 7, 1976, discloses a control system to detect the stroke of a depressed acceleration pedal and the number of revolutions of an engine in order to control a cooling compressor, such that no power is supplied from the engine to the compressor when the revolution number is not increased in accordance with the stroke of the depressed acceleration pedal.
With such a control system, however, the compressor is to be stopped when the vehicle is traveling up a relatively long upward slope too.
In vehicles which are equipped with an automatic transmission including a fluid coupling, particularly such as a torque converter, when a cooling air conditioner is operated, the startability as well as the performance of acceleration of the vehicle is greatly affected by the air conditioner compressor for the following reasons:
(1) A fluid coupling generally has a very poor transmission efficiency of almost zero percent in the vicinity of a stalling point of an engine or in the vehicle speed range near zero. Thus, when a fluid coupling is used, the energy of acceleration inherently transmitted to a tire is reduced in such a range.
(2) In general, the energy for driving the compressor is in proportion to the number of revolutions, while the stalling revolution number of the automatic transmission is relatively high. Thus, more energy is consumed by the compressor in a vehicle with an automatic transmission than compared with a vehicle with a manual transmission.
Accordingly, in a control system of a vehicle equipped with an automatic transmission and an air conditioner, it is first of all desired to accurately detect the state of acceleration to control the shutdown of a compressor and, besides, for the system to perform a controlled shutdown of the compressor also when accelerated to pass another vehicle.
Some automatic transmissions employed an electronic control for setting of characteristics as well as for accuracy. Such an electronic type automatic transmission generally includes a shift map which ordinarily has an abscissa representing the vehicle speed (V), and an ordinate representing a parameter representative of engine output, such as the opening of a throttle (Th). Such a shift map is able to clearly indicate the range of adequate regions for starting and accelerating the vehicle.
In the accompanying drawings, FIG. 7 is a typical example a shift map that is used in an ordinary electronic control type automatic transmission having three forward speeds.
In FIG. 7, the abscissa represents the vehicle speed V, and the ordinate the throttle opening Th. Shown by thick lines X and Y are the boundary between a first speed zone and a second speed zone and between the second speed zone and a third speed zone respectively. Designated at reference character A.sub.1 is a region for starting and accelerating a vehicle, where the automatic transmission is set at a shift position of the first speed, A.sub.2 is a region for ordinary accelerating operations such as passing another vehicle which is usually performed after a shift-down from the third speed to the second speed, and A.sub.3 is a region for normal acceleration performed in third speed by lightly depressing an acceleration pedal of the vehicle. On the map, each instaneous control point is identified as a coordinate (Vd, Thd) of respective instantaneous values of the vehicle speed V and throttle opening Th. For example, when the vehicle is traveling on a steep or gentle long upward slope at a constant speed, adequate control points are to be found in the region A.sub.2 or A.sub.3 in accordance with respective instaneous values Vd, Thd.
The present invention has been achieved to successfully substantiate such a desideratum as described in conjunction with conventional control system for engine-driven auxiliary equipments such as air conditioners for vehicles. Particularly, it is achieved from a view point that such desideratum is characteristic to vehicles of the type which includes an electronic control type atuomatic transmission having a fluid coupling, and where in general a shift map is advantageously utilized in such an automatic transmission.